Understanding Emission Factors for Carbon Footprint Calculations

Emission factors form the core of carbon footprint calculations. By multiplying them with the activity variable – any activity generating emissions – the result is a carbon footprint.

But where can suitable emission factors be found? And why there are many options to choose from for the same products? Let’s delve deeper into this.

Accurate results come with better data

Everyone conducts carbon footprint calculations for the first time at some point. Initially, it can feel like a daunting task, lacking confidence in one’s own work or the accuracy of the calculations.

Researchers refer to carbon footprint calculations as assessments of climate impacts because the resulting figures are always estimates. While more precise information can be obtained through physical measurements, in most cases, computational estimates are sufficient.

However, the results of calculations can be refined by using more precise emission factors. At Biocode, we categorize emission factors into four classes:

Generic

Those extracted from an emission factor database, scientific research, or other reliable publications. For example:

• Strawberry, fresh 0.45 kg CO₂e/ kg

Reference values

Slightly more specific than generic ones, for example the production country or method can be specified. For example:

• Strawberry, fresh, field grown in Finland 0.41 kg CO₂e/ kg

Modified

Derived from a company’s supply chain or tailored to better reflect specific processes. For example:

• Strawberry, fresh, organic certified, 2022, Finland 0.39 kg CO₂e/ kg 

Modeled

Developed through modeling processes. For example:

•  Strawberry, fresh, organic certified, Hannula’s farm, 2022, Finland 0.40 kg CO₂e/ kg

Typically, the first carbon footprint calculations are done using generic emission factors, with progression toward more precise factors as expertise grows. A good guideline is to calculate activities with the greatest climate impacts using the most accurate emission factors possible.

Calculated carbon footprints can also serve as emission factors. For instance, the carbon footprint of frozen strawberries can be used to calculate strawberry jam’s carbon footprint. In practice, therefore, emission factors and carbon footprints refer to the same thing.

Modeling emission factors

Various methods are used in the modeling process, for instance, the Intergovernmental Panel on Climate Change (IPCC) has issued numerous modeling guidelines for different categories.

There are also other modeling methods, and results obtained through different means may differ, making comparisons challenging. Sometimes, calculation methods are not publicly disclosed, although transparency is crucial for enabling comparisons.

Various guidelines, standards, and protocols aim to standardize calculation methods. In Finland, The Natural Resources Institute (Luke) is developing consistent guidelines for modeling emissions and life cycle assessments through the LCAFoodPrint project.

Modeling raw materials in the food industry

In the food industry, raw materials account for the majority of a company’s and product’s carbon footprint. The GHG Protocol encourages calculating the largest emission sources based on primary data, prompting food companies to often model emission factors together with primary producers. This provides a more accurate picture of their own processes and resulting emissions.

By calculating emissions from primary production, an emission factor for the raw material can be derived. In other words, a precise emission factor based on primary data for a raw material is obtained by calculating emissions from cultivation and animal production.

Emissions calculations include at least the following areas: fossil and biogenic emissions, potential removals, and emissions from land use and its changes.

• Cultivation
• Field Nitrous oxide emissions
• Processing
• Land use carbon footprint
• Animals
• Feeds
• Manure
• Energy
• Transportation

Up-to-date emission factors and carbon footprint calculations

It’s advisable to start carbon footprint calculations even without precise knowledge of which emission factor to use. Calculations can always be refined as information increases, and emission factors can be adjusted or modeled for the next year’s calculations.

In such cases, it’s important to describe why the emission factor has changed.

Emission factors in general databases are constantly updated. Three years is generally considered a cutoff for ensuring emission data is up-to-date. After that, emission factors used in the calculations should be checked. And of course, if there are changes in operations and descriptors have changed along the way, the calculation should be repeated.

For instance, corporate emission calculations are done annually because company operations are constantly changing. This is also when the timeliness of emission factors is checked.

Product carbon footprint calculations should be renewed at least when there are changes in production inputs, such as transportation distances, raw materials, or changes in production energy sources, or when a more precise emission factor has been modeled. Otherwise, at least every three years.